Air cooled light projection unit

ABSTRACT

An air-cooled light projection unit for use in apparatus in which film is exposed to light, such as apparatus for projecting or duplicating film images. A heat-radiating light source is enclosed in a housing from which light is projected toward a film located at an illumination station. Walls within the housing define a tortuous cooling passageway through the housing. The passageway extends first past the illumination station between the film and the light source and secondly past a heat radiating portion of said light source. Blowers are associated with the housing for causing a flow of cooling air through the passageway. A method performed by the projection unit is disclosed in which cooling air is introduced into the light projection unit, directed past the illumination station between the light source and the film, and past a heat-emitting portion of the light source. The cooling air is then emitted from the light projection unit.

United States Patent [191 Kitch Oct. 2, 1973 1 i AIR-COOLED LIGHTPROJECTION UNIT [75] Inventor: Paul E. Kitch, West Springfield,

Hampden County, Mass.

[73] Assignee: Scott Paper Company, Philadelphia,

221 Filed: Apr. 26, 1971 21 Appl. No.: 137,316

[51] Int. Cl. G03b 27/52 [58] Field of Search 353/53-61; 240/47;352/146, 202; 355/30, 110

[56] References Cited UNITED STATES PATENTS 3,202,070 8/1965 Pratt, Jr.et a1 355/100 3,554,638 1/1971 Dimitracopoulos. 353/57 X 3,408,13810/1968 Harz et al. 352/146 X 2,362,601 11/1944 Wengcl l 353/612,248,052 7/1941 Auchincloss et al..... 353/52 X 3,168,985 2/1965 Troupet a1. 240/47 X 3,318,184 5/1967 Jackson 352/202 X 3,494,693 2/1970Elmer 353/55 FOREIGN PATENTS OR APPLICATIONS 573,700 12/1945 GreatBritain 353/54 Primary Examiner-Samuel S Matthews AssistantExaminerRichard M. Sheer Attorney-William J. Foley, Martin L. Faigus,John W. Kane, Jr., John A. Weygandt and R. Duke Vickrey 57 ABSTRACT Anair-cooled light projection unit for use in apparatus in which film isexposed to light, such as apparatus for projecting or duplicating filmimages. A heat-radiating light source is enclosed in a housing fromwhich light is projected toward a film located at an illuminationstation. Walls within the housing define a tortuous cooling passagewaythrough the housing. The passageway extends first past the illuminationstation between the film and the light source and secondly past a heatradiating portion of said light source. Blowers are associated with thehousing for causing a flow of cooling air through the passageway. Amethod performed by the projection unit is disclosed in which coolingair is introduced into the light projection unit, directed past theillumination station between the light source and the film, and past aheat-emitting portion of the light source. The cooling air is thenemitted from the light projection unit.

2 Claims, 11 Drawing Figure INVENTOR. PAUL E. KITCH PATENTEDUBT 2AIR-COOLEI) LIGHT PROJECTION UNIT BACKGROUND OF THE INVENTION 1. Fieldof the Invention The present invention relates to improvements inapparatus in which film is exposed to light, such as apparatus forprojecting or duplicating film images, and particularly to a new andimproved air-cooled light projection unit for use in such apparatus.

2. Brief Description of the Prior Art There are many different forms ofapparatus in which film is exposed to light emitted from a closelyspaced light source. Such light sources generally generate and radiate aconsiderable amount of heat as well as light, due to the fact that largequantities of power must be utilized to create light of sufficientlyhigh intensity to accomplish the intended purpose. For example, wherethe light generated is used to project a film image onto a remotelypositioned surface such as a screen, light of very high intensity mustbe generated since the light intensity dininishes in an amountproportional to the square of the distance between the light source andthe remote surface on which the image is to be displayed or projected.

In addition, for certain purposes, it is also required that the lightsource be closely spaced to the film containing an image to beprojected. This is particularly the case in film duplication apparatusin which the image on a master film is transferred to a duplicating filmby light passing through the imaged master film when it is in contactwith the duplicating film. Such a process involves the activation of aphotosensitive layer on the duplicating film, which may be of any one ofa number of different types known to those skilled in the art.Regardless of the type of film system employed, this rate of thisactivation is generally responsive to the intensity of the lightstriking the photosensitive layer on the film and accordingly, a lightsource is generally placed quite close to the duplicating film in orderto maximize the speed of film duplication and to make the processcommercial, as well as to optimize the duplication process itself fromthe photographic quality standpoint.

However, one of the problems experienced with such film projection andfilm duplication apparatus has been the damage caused to the film orfilms when the heat radiated by the light source exceeds a certainamount, which often occurs when the apparatus has been in operation fora considerable period of time and heat builds up to a high temperature.Where the film material constitutes the only copy of such imageinformation, as is usually the case where a master film is involvedwhich is being used to make a duplicate copy, the loss or damage of thisinformation due to excessive heating of the film and distortion,blistering or melting of the film can be extremely expensive and costlyand in many cases, causes irreparable damage.

In addition, high intensity light sources utilized in such apparatus aregenerally of an electrical type and comprise extremely expensiveelements of the apparatus. It has been found that when such lightsources are operated at high temperatures or in a high temperatureenvironment, their operating life is severely curtailed. The cost ofreplacing such light sources constitutes a significant portion of thecost of operation of such apparatus. However, when such light sourcesare operated in a cooler environment, their operating life issubstantially increased, thereby reducing the cost of operating suchapparatus.

In view of the above-mentioned difficulties and shortcomings, it hasbeen discovered that the operating life of a light source can be greatlyextended by cooling the light projection unit in which it is mounted.Furthermore, such an arrangement is also advantageous in re ducing oreliminating risk of heat damage to the film being projected orduplicated.

Accordingly, it is a chief object and advantage of the present inventionto eliminate the damage previously caused by a heat-radiating lightsource in a light projection unit. It is a further object and advantageof the present invention to greatly extend the operating life of thelight source in a light projection unit.

SUMMARY OF THE INVENTION The invention is an air-cooled light projectionunit for use in apparatus in which film is exposed to light. The unitincludes a heat-radiating light source which directs light toward a filmat an illumination station. The light source is at least partiallyenclosed by a housing which defines an opening through which light isprojected toward the film at the illumination station. Wall means withinthe housing define a tortuous passageway through the housing. Thepassageway includes a first portion extending past the illuminationstation, between the film and the light source, and a second portionconnected to the first portion and extending past a heat-radiatingportion of the light source. Means are associated with the housing forcausing a flow of air through the passageway from the first portion tothe second portion. In some embodiments, the apparatus includes blowersat either or both ends of the passageway to create the flow of airtherethrough. In a preferred embodiment, the light source is located infront of an arcuate reflecting element within the housing, and twospaced reflecting elements divergingly extend from the light sourcetoward the illumination station in order to more efficiently concentrateand redirect divergent rays of light toward the illumination station. Aplate, at least a portion is transparent, extends between the divergentends of the two spaced reflecting elements. A wall within the houseconnects the side of the housing to one of the two spaced reflectingelements to form a portion of the passageway, and another wall extendsfrom the housing to the arcuate reflecting element to define anotherportion of the passageway.

In a particular embodiment, the invention comprises an improvement inapparatus for duplicating film, wherein a master film and a duplicatefilm are brought into overlying relationship with one another and lightis projected through the master film and onto the duplicate film at anillumination station. In that instance, the heat-radiating light sourcemust be of relatively high intensity in order to accomplish filmduplication at commercial speeds. In addition, it must be placed fairlyclose to the film in order to further maximize the intensity of thelight striking the film.

The invention also includes a method for cooling a light projection unithaving a heat-radiating light source which directs light toward a filmat an illumination station. In the method, cooling air is introducedinto the light projection unit and directed past the illuminationstation between the light source and the film. The cooling air is thendirected past a heat-radiating portion of the light source when itissues from the illu mination station. The cooling air is then emittedfrom the light projection unit.

DESCRIPTION OF THE DRAWING The above-mentioned and additional objectsand advantages of the present invention will become apparent from thefollowing description thereof, taken in conjunction with the drawingwhich is a sectional side elevation view of one form of microfilmduplication apparatus which includes one embodiment of the air-cooledlight projection unit of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The drawing shows aportion of one form of film duplicating apparatus in which theair-cooled light projection unit of the present invention isincorporated. The film duplicating apparatus includes a rotatablymounted support cylinder on the surface of which an unimagedphotosensitive duplicating film 11 is supported. An original master film12, that is, a lightstable, previously exposed film which alreadycontains a developed visible image, is superimposed upon the duplicatingfilm 11. The films 11 and 12 are supported in this manner and run incontact with one another and the surface of the support cylinder 10through about 270 of rotation of the support cylinder 10. Theduplieating film 11 is fed onto the support cylinder 10 from a feed reel13 and after it passes around a guide roller 14, a guide roll 15 and aguide roller 16.

The duplicating film 11 is of a nature such that it is photosensitive,so that when it is exposed to a lightshadow image, as by transmission oflight through the master film onto the duplicating film, a developableimage will be created on the duplicating film. Upon leaving the supportcylinder 10, the duplicating film 11 passes around a guide roller 17 andadvances through an opening 18 in the dividing wall or partition 20 andinto the developing chamber 21 where it is developed in accordance withwell-known techniques, the nature of which depends upon the type of filmsystem employed. The duplicating film 11, for example, may be of aconventional silver halide form or of a conventional diazo form, thenature of each being well-known to those skilled in photography andcopying.

The drawing shows the type of developing chamber commonly employed fordeveloping a diazotype film, in which the film is exposed to ammonia gasformed by volatilizing an aqueous ammonia solution by heating means (notshown) to develop the image thereon. To insure exposure of the film toammonia for a sufficient time while it is continuously fed into thechamber 21, a substantial length of the film is accumulated within thechamber 21 by running it between a plurality of rollers 22 to createmany stretches of the film which permit exposure of the film surface tothe atmosphere in chamber 21. The developed film is fed through a secondopening 23 in dividing wall 20 and is passed over guide roll 24, guideroll 25, and guide roll 26, after which it is wound upon a takeup reel27.

The imaged master film 12 is fed from a supply reel 28 around a snubbingroller 29, and then around a guide roller 30, after which it is fedaround the periphery of the support cylinder 10 on top of theduplicating film 11. Upon leaving the support cylinder 10 and theduplicating film II, the master film 12 is fed around a guide roller 31and then around a snubbing roller 32,

around guide roller 33 and onto a takcup reel 34. The entire film systemis driven by a drive motor (not shown) operably connected by a belt (notshown) to pulleys (not shown) on certain of the guide rollers and reels,such as the two takeup reels 27 and 34, as are necessary to advance theduplicating film I1 and the master film 12 through the apparatus.Therefore, it is tension on the films 11 and 12 and friction between theouter periphery of the driven rollers and the films which advances theduplicating film l1 and the master film 12 around the support cylinder10 and through the duplicating apparatus. These details have beenomitted to avoid obscuring the invention, but the details of such adrive arrangement would be readily apparent to one skilled in the art.

The side wall 36 of the duplicating apparatus has an opening 37 thereinradially disposed from the support cylinder 10. A light chamber 38 isformed by spacedapaxt upper and lower inclined walls 40 and 41,respectively, radially extending from the side wall 36 at the top andbottom of the opening 37 to a point closely spaced from the surface ofthe support cylinder 10 and side walls 42, only one of which is shown,which connect the respective ends of upper and lower walls 40 and 41 togenerally define an exposure station, indicated generally by the bracket43. Thus, exposure of the duplicating film 11 to light projected throughthe master film 12 only occurs when the films 11 and 12 pass over thesupport cylinder 10 between the lower side wall 41 and the upper sidewall 40.

A lamp 44 is spaced from the side wall 36 in line with the opening 37therein. The lamp 44 is partially enclosed by an arcuate reflectingelement 45 and outwardly diverging upper and lower reflecting elements46 and 47, respectively, spaced apart from one another. All of thereflecting elements 45, 46 and 47 combine to project light from the lamp44 through the opening 37 into the light chamber 38 and through themaster film 12 onto the duplicating film 11 as they move through theexposure station 43. The lamp 44 may comprise any of the high intensityelectric light sources typically employed in film projection apparatusand film duplicating equipment.

A shutter 50 is disposed adjacent the side wall 36 and the opening 37therein, and is movable from an open position where it is adjacent theside wall 36 as shown in FIG. 1 in solid line, to a closed positionwhere it is in front of the opening 37 and is in front of the spacebetween the reflecting elements 46 and 47, as shown in phantom line inFIG. 1. In the open position, light from the lamp 44 can strike thefilms 11 and 12 at the exposure station 43, but in the closed position,light which enters the light chamber 38 is essentially precluded fromstriking the films 11 and 12 at the exposure station 43. Movement of theshutter 50 is accomplished by a rack and pinion mechanism, the shutter50 being attached to the lower end of the rack 51 which is meshed withand driven by a pinion gear 52 which is attached to the drive shaft of ashutter drive motor 53. The shutter drive motor 53 is a reversible ACmotor and the direction of its operation may be controlled by a simpleswitch (not shown) or by more automatic means (not shown), thearrangement and operation of which would be understood by those skilledin the art.

A pressure roller 54 is disposed within the light chamber 38 andarranged to contact the surface of the master film 12 to press itagainst the duplicating film 11 just prior to the point where the films11 and 12 are struck by light. This pressure substantially eliminatesany air gaps between the two films 11 and 12 and ensures uniform contacttherebetween which is essential to avoid undercutting of the imageduring exposure. In the duplication of images, and particularlymicroimages on microfilm, close contact during exposure to light isextremely important to avoid the loss of resolution which otherwiseoccurs due to non-radial light rays passing through the imaged film.Such diverging light rays tends to undercut the image on the master film12 if the master film 12 and the duplicating film 11 are not in closecontact with one another.

The pressure roller 54 is rotatably mounted on one end of a pivotablymounted support arm 55 which pivots about a pin 56 connected to the sideplate 42. The other end of the support arm 55 is connected by a tensionspring 57 to the back side of the lower reflecting element 47. From thisarrangement, it can be seen that the pressure roller 54 is spring-biasedinto contact with the master film 12 when the shutter 50 is opened. Inaccordance with the invention, the pressure roller 54 is moved away fromand out of contact with the master film 12 when the shutter 50 is movedto its closed position. This is accomplished by the lower end of theshutter 50 striking the support arm 55 holding the pressure roller 54and overcoming the force of the spring 57 by the force of the shutterdrive motor 53 operating through the rack 51 and pinion gear 52 so thatthe pressure roller 54 is pivoted out of contact with the master film12. This position of the support arm 55 and pressure roller 54 is shownin phantom in the drawing.

The lamp 44 and reflecting elements 45, 46 and 47 are enclosed within ahousing formed by walls 60, 61 and 62, and spaced side walls 63, onlyone of which is shown in the drawing. The resulting housing is openalong its side directed toward the opening 37 and the support cylinderso that light from the lamp 44 may be directed onto the film 11 and 12carried over the support cylinder 10 when the shutter 50 is in its openposition.

One of the problems experienced with this type of arrangement in thepast has been the excessive buildup of heat within the housing andwithin the light chamber 38 through which the films 11 and 12 pass. Thisheat which results primarily from the unusually high intensity lightsource 44 is required for film duplication and particularly for theduplication of microfilm at high speeds. The result of such a buildup ofheat is to temporarily distort the film and often permanently damage thefilm by blistering or melting it. In addition, the high temperaturesgreatly shorten the life of the lamp 44, resulting in the expense ofreplacing the lamp.

In accordance with the present invention, a passageway is formed throughthe housing through which cooling air is circulated to cool specificallyboth the'region between the lamp 44 and the films 11 and 12 and theregion behind the lamp in order to greatly improve the operation of thefilm duplication apparatus. This cooling reduces or eliminates any riskof damage to the films 11 and 12, and enables the lamp 44 to operate ina cooler environment, thereby greatly prolonging its life. In theapparatus shown in the drawing, the upper and lower reflecting elements46 and 47 extend into contact with the lamp 44. A partition 64 extendsfrom the lower reflecting element 47 to the back wall 61 of the housingand defines a first duct between the lower side wall 60 of the housingand the partition 64 and the reflecting element 47.

A glass plate 65 extends from one end of upper reflecting element 46 toone end of lower reflecting element 47 to separate the lamp 44 from thefilms I1 and 12 and to somewhat reduce the amount of heat radiating fromthe lamp 44 toward the films. A passageway or duct is thus formedbetween the light source 44 and the films 11 and 12 which connects withthe passageway described previously. This duct is present regardless ofthe position of the shutter St). However, when the shutter 50 is closedand covers the opening 37, cooling air directed through the passagewaypast the illumination station 43 is excluded from the light chamber 38and from contact with the films 11 or 12. However, it cools the shutter50 and the glass plate 65.

The arcuate reflecting element 45 is connected by a wall 66 to the upperwall 62 of the housing so as to fur ther define a passageway between thereflecting element 46, the light source 44 and a portion of reflectingelement 47 and the upper wall 62, wall 66, and reflecting element 45.The passageway thus described extends beyond the light source 44. Itthen turns and extends toward an outlet through the upper wall 62. Theabovedescribed passageways form one continuous tortuous passagewaythrough the housing which allows both the region between the lightsource and the films, and the region behind the light source, to becooled.

A blower 68 is connected to lower wall 60 of the housing so as to blowcooling or ambient air into the tortuous passageway thus describedthrough the housing 70 and lower wall 60. Inlet air enters the apparatusthrough an opening 73 in the end wall 74. The cooling air is directedpast the illumination station between the light source 44 and the film12. It then is directed past a heat-radiating portion of the lightsource. Preferably the cooling air is first directed past the regionbetween the light source 44 and the films since that region is generallycooler than the heat-radiating portion of the lamp 44. In this manner,the coolest air operates on the coolest elements, thereby obtainingmaximum heat removal efficiency in true countercurrent fashion. As theair passes through the passageway thus described, it first removes heatfrom the region between the films and the glass plate 65, and thenremoves heat from the heat-radiating back side of the lamp 44 and fromthe reflecting elements 45, 46 and 47 which tend to become heated duringoperation of the apparatus. The cooling air then passes through anopening 67 of upper wall 62 of the housing and into a duct 71 whichconnects with a second blower 72. Blower 72 emits the cooling air, whichat this point is at a higher temperature than when it entered the lightprojection unit. through an opening in the end wall 74.

ln view of the above description of the invention and of the drawings,it can be seen that the invention provides a new and improved method andapparatus for use in instances where film is exposed to light, andparticularly in film projection and film duplication apparatus in whichthe above-mentioned problems have previ ously been experienced. It alsocan be seen that the aircooled light projection unit of the presentinvention overcomes many of the problems which have been ex periencedpreviously in such apparatus, such as damage or distortion of the filmdue to heat from the light source which, because of the requirements forlight of unusually high intensity, radiates a considerable quantity ofheat. In addition, by operating the light source in a coolerenvironment, which is provided by the apparatus of the presentinvention, the operating life of the light source is substantiallyincreased.

From the above description of the invention, it will be apparent thatvarious modifications in the method and apparatus described in detailherein may be made within the scope of the invention. For example, thetortuous passageway might be of a substantially different configurationthan that shown and described above so long as the cooling air isdirected through the illumination station between the light source andthe film, and also past a heat-radiating portion of the light source,Thus, it is this combination of cooling steps which has been found toresult in maintaining the environment within the housing much coolerthan that in similar light projection units utilized in the past.Therefore, the invention is not to be limited to the specific details ofthe method and apparatus described herein except as may be required bythe following claims.

What is claimed is:

1. Apparatus for duplicating film, wherein a master film and a duplicatefilm are brought into overlying relationship with one another and lightis projected through said master film and onto said duplicate film at anillumination station, comprising a heat radiating light source whichdirects light toward said films when they are disposed at saidillumination station,

a housing at least partially enclosing said light source,

said housing defining an opening through which light is projected towardsaid films at said illumination station,

wall means within said housing which define a tortuous passagewaythrough said housing, said passageway including a first portionextending past said illumination station between said film and saidlight source, and

a second portion connected to said first portion and extending past saidheat-radiating light source, said wall means including,

two spaced-apart reflecting elements extending and diverging from saidlight source toward said illumi nation station, and

a transparent plate extending between and joined to the divergent endsof said two reflecting elements, said first portion of said passagewayextending past only the side of said plate opposite said heatradiatinglight source, and

means associated with said housing for causing a flow of cooling airthrough said passageway from said first portion to said second portion.

2. Apparatus for duplicating film according to claim 1, wherein saidmeans associated with said housing for causing a flow of cooling airthrough said passageway comprise a first blower for introducing saidcooling air into said first portion of said passageway, and a secondblower for exhausting said cooling-air from said second portion of saidpassageway.

1. Apparatus for duplicating film, wherein a master film and a duplicatefilm are brought into overlying relationship with one another and lightis projected through said master film and onto said duplicate film at anillumination station, comprising a heat radiating light source whichdirects light toward said films when they are disposed at saidillumination station, a housing at least partially enclosing said lightsource, said housing defining an opening through which light isprojected toward said films at said illumination station, wall meanswithin said housing which define a tortuous passageway through saidhousing, said passageway including a first portion extending past saidillumination station between said film and said light source, and asecond portion connected to said first portion and extending past saidheat-radiating light source, said wall means including, two spaced-apartreflecting elements extending and diverging from said light sourcetoward said illumination station, and a transparent plate extendingbetween and joined to the divergent ends of said two reflectingelements, said first portion of said passageway extending past only theside of said plate opposite said heat-radiating light source, and meansassociated with said housing for causing a flow of cooling air throughsaid passageway from said first portion to said second portion. 2.Apparatus for duplicating film according to claim 1, wherein said meansassociated with said housing for causing a flow of cooling air throughsaid passageway comprise a first blower for introducing said cooling airinto said first portion of said passageway, and a second blower forexhausting said cooling-air from said second portion of said passageway.